The two kidneys are positioned at the back of the abdomen below the diaphragm, and are slightly larger than the fist of their owner. The diagram below shows where they are positioned and how they are connected to the blood system. Their function is to remove waste products, chiefly the waste product of deamination, urea, from the blood stream and to maintain the correct balance of water within the body.

Blood enters the kidney through the Renal artery. After filtration, the blood leaves the kidney through the Renal vein. The waste products of filtration leave the kidney through a tube called the Ureter and pass down to the bladder where the liquid, now called Urine is stored. Finally the urine leaves the bladder through a tube called the Urethra.

Terminology: Deamination.... the process of breaking down amino acids which takes place in the liver. Amino acids are the sub-units of proteins and contain Nitrogen which must be excreted and energy which the body can utilise, so they are not excreted directly. Enzymes breakdown the amino acid to form ammonia (which contains the Nitrogen and is toxic) and acid which is converted into carbohydrate or fat for energy storage. The ammonia is rapidly converted into less toxic urea. Watch the animation of deamination below!